JPS6355914A - High frequency magnetic field generating and detecting device - Google Patents

Abstract

PURPOSE:To continuously adjust the resonant frequency of an LC series resonant circuit by a method wherein a variable capacitor is constituted by moving one of the superposed T-shaped conductive plates through the intermediary of a dielectric material and by changing electrostatic capacitance. CONSTITUTION:An E-shaped conductive plate 1H is formed by superposing two T-shaped conductive plates T1 and T2 through the intermediary of a dielectric material 4. The dielectric materiel 4 is a synthetic resin polymer and it is fixed to the outside of the T-shaped conductive plate T1 or the inside of the T2, and a variable capacitor 5 is constituted. When either of said T-shaped conductive plates is moved in vertical direction, the electrostatic capacitance of the variable capacitor 5 is changed, and the resonant frequency of the microwave circuit, constituting an equipment LC series resonant circuit together with the variable oapacitor 5, is adjusted continuously. Also, the efficiency in generation of a transmitting magnetic field can be improved by forming the high frequency coil to be used for the whole body into an oval shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency magnetic field generator/detector, particularly to a high frequency magnetic field generator/detector used in a nuclear magnetic resonance apparatus.

[Conventional technology]

Figure 9 shows, for example, ``Journal of Magnetics''.
Resonance (Journal of Magnet)
icReθonance) J Vol. 36, pages 447 to 451 (19'79) is a perspective view showing a conventional high frequency magnetic field generator/detector, in which (1) is an H-shaped A vertical band is a coil in which a pair of conductive plates, such as copper plates, are arranged symmetrically to form a hollow cylindrical body.
nd) and a non-protruding part (1a) called wing (w
It has a protrusion (1b) called . (
2) is a chip capacitor inserted between opposing wings (11)). (3) is an electric field shielding plate placed inside the wing (1b) via an insulating layer (not shown) and in the same manner as a pair of H-shaped conductor plates (1).
They are a pair of conductor rings, one conductor ring (3a) being called the top guard ring and the other conductor ring (3b) being called the bottom guard ring.

Note that at least one of the conductor rings (3) is at ground potential.

A conventional high-frequency magnetic field generator/detector is configured as described above, and includes a conductor plate (1), a chip capacitor (2), and a conductor ring (
3) forms a three-dimensional circuit that equivalently functions as an LO series resonant circuit. As mentioned above, the conductor ring (3) is used for electric field shielding, that is, for reducing dielectric loss within the measurement object due to the generated electric field when the measurement object is installed in the high-frequency magnetic field generator/detector.

[Problem that the invention seeks to solve]

Do conventional high-frequency magnetic field generators and detectors resonate? The capacitance of the chip capacitor used for this purpose is fixed, and in order to change or fine-tune the resonance frequency, it is necessary to replace the chip capacitor with a different capacitance, which is a practical problem.

This invention has been made to solve these problems, and aims to provide a high-frequency magnetic field generator/detector that can continuously change the resonant frequency. Conventionally, high-frequency coils for the whole body were cylindrical. Because it was a type,
The efficiency of transmitting magnetic field generation is low, and the S/N of the received signal (
There were problems such as a relatively small signal to number ratio.

[Means for solving problems]

The same-frequency magnetic field generator/detector according to the present invention generates two T-shaped conductive plates by moving one of the two T-shaped conductive plates stacked on top of the other with a dielectric material in between. It incorporates a variable capacitor that changes the capacitance by changing the overlapping area.

Furthermore, the shape of the whole-body high-frequency coil is made into an elliptical shape. [Function] In this invention, since the variable capacitor is incorporated, the resonant frequency of the LC series resonant circuit can be continuously varied.

Furthermore, by making the whole body high-frequency coil elliptical, the efficiency of generating the transmitting magnetic field and the SA of the received signal are improved.

〔Example〕

FIGS. 1, 2, and 3 are a perspective view, a cross-sectional view, and an equivalent circuit diagram showing an embodiment of the present invention, respectively, in the case where the high-frequency coil is cylindrical. In this invention, two T-shaped conductor plates (T1) and (T2) are overlapped with each other with a dielectric material (4) in between, thereby forming one H-shaped conductor plate similar to that shown in FIG. A prison conductor plate (1H) is formed. Other than this point (la), (lb), (21, (31).

(3a) and (3b) are exactly the same as described with respect to FIG. The dielectric material (4) is fixed to the outside of one T-shaped conductor plate (T1), that is, to the outside of the vertical band (1a) on the upper side of the H-shaped conductor plate (1H), or as shown in FIG. The other T-shaped conductor plate (T2) as shown
, that is, the lower side of the H-shaped conductor plate (1H)
It is fixed inside the band (1a) and is made of porcelain or a synthetic resin polymer such as polytetrafluoroethylene. The variable capacitor (5) consists of two T-shaped conductor plates (T1) and (T2) as described above and a dielectric material (4), for example, one T-shaped conductor plate (T1) is connected to the other. T of
Its electrostatic capacity can be changed by moving it relative to the letter-shaped conductor plate (T2). In this way, in this invention, the electrostatic response of the variable capacitor (5) can be changed by smoothly moving either the 10,000 T-shaped conductive plate (T1) or (T2) in the vertical direction in FIG. Therefore, along with the variable capacitor (5), the equivalent L
The resonant frequency of the three-dimensional circuit constituting the C series resonant circuit can be continuously adjusted. FIG. 4 is a perspective view showing a modification of the embodiment shown in FIGS. This is an example using an H-shaped conductor plate (1H).

FIG. 5 is a perspective view showing another embodiment of the present invention, which differs from the embodiment shown in FIGS. 1 to 3 in the electrical connection of the protrusion or wing (1b), and has a chip capacitor. Instead of capacitive coupling in (2), the wings (1b) are electrically connected by pressure contact or soldering. Although not shown, the wing (1b) may be electrically connected to the capacitively coupled chip capacitor (2) using a conducting wire or a conductor.

FIG. 6 is a perspective view showing a modification of the embodiment shown in FIG. 5, and is similar to FIG. 4.

In FIGS. 5 and 6, a case with a card ring is shown, but it is not necessary.

FIGS. 7 and 8 are perspective views showing other embodiments of the present invention, in which the high-frequency coil has an elliptical cylindrical shape, (1)
~1lo) are the same as the embodiment of FIG. FIG. 7 shows an example in which the vertical bands are arranged in the short axis direction of the ellipse, and FIG. 8 shows an example in which they are arranged in the long axis direction.

In addition, the cylindrical high-frequency magnetic field generator/detector for the whole body has become Daisei.1. Efficiency of transmitting magnetic field generation or 8/N of received signal
becomes smaller. Since the cross section of the human body is approximately elliptical, the -frequency magnetic field generator/detector can be formed into an elliptical cylinder whose major diameter is the diameter of the cylinder. This results in higher efficiency in magnetic field generation than in the case of a cylinder, and 8/8 of the received signal.
N also improves.

For example, it has been found through experiments that for 64 MHz, the transmitted magnetic field increases by 60 to 70% in the case of an elliptical shape and the same transmit power as compared to the case of a cylinder.

Also, when the RF coil is installed so that the long axis direction of the ellipse is horizontal, the vertical band can be created in the short axis direction, depending on whether the high frequency magnetic field is generated horizontally or vertically.
[Effects of the Invention] As described above, according to the present invention, two T-shaped conductive plates are overlapped with each other via a dielectric material, and one of the two T-shaped conductive plates is By moving one side relative to the other, the variable capacitor 4 is formed, so that the resonant frequency of the LCi column resonant circuit can be freely adjusted, which has the effect of being able to cope with a wide range of magnetic fields.

Moreover, by making the shape of the high-frequency magnetic field generator/detector for the whole body into an ellipse, the efficiency of magnetic field generation is high, and the S/N of the received signal is also improved.

[Brief explanation of drawings]

1, 2, and 3 are respectively a perspective view and a sectional view 9 equivalent circuit diagram showing an embodiment of the present invention, FIG. 4 is a perspective view showing a modification of the above embodiment, and FIG. 5 is a perspective view showing an embodiment of the invention. FIG. 6 is a perspective view showing a modification of the other embodiment, FIG. 7 is a perspective view showing another embodiment of the invention, and FIG. 8 is a perspective view showing another embodiment of the invention. A perspective view showing another embodiment of the invention, FIG. 9 is a conventional high frequency magnetic field generator/detector? FIG. (IH) is an H-shaped conductor plate, (1a) is a vertical band, (1b) is a wing, (T1) and (T2) are T
(2) is a chip capacitor, (3) is a conductor ring, (4) is a dielectric material, and (5) is a variable capacitor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (10)

[Claims] (1) One H-shaped conductor plate is formed by overlapping two T-shaped conductor plates via a dielectric material, and at least one pair of H-shaped conductor plates is arranged symmetrically. a three-dimensional circuit configured by forming a hollow cylindrical body by electrically connecting the opposing protrusions of the at least one pair of H-shaped conductor plates; and the two T-shaped conductor plates. A high frequency magnetic field comprising a variable capacitor configured by moving one of the plates relative to the other, wherein the three-dimensional circuit equivalently constitutes an LC series resonant circuit together with the variable capacitor. Source/detector. (2) The three-dimensional circuit includes a pair of conductor rings installed concentrically with at least one pair of H-shaped conductor plates and inside the protrusion of the plate with an insulating layer interposed therebetween, and at least one conductor ring is grounded. The high-frequency magnetic field generator/detector according to claim 1, characterized in that the high-frequency magnetic field generator/detector is set to a potential. (3) The high-frequency magnetic field generator/detector according to claim 1 or 2, wherein the three-dimensional circuit is cylindrical. (4) The high-frequency magnetic field generation system according to claim 1 or 2, characterized in that the three-dimensional circuit has an elliptical cylindrical shape.
Detector. (5) The high frequency magnetic field generator/detector according to claim 1, wherein the electrical connection of the protrusion is capacitive coupling using a chip capacitor. (6) The high frequency magnetic field generator/detector according to claim 1, wherein the electrical connection of the protrusion is made by pressure contact or soldering. (7) The high-frequency magnetic field generator and detector according to claim 1, wherein the electrical connection of the protruding portion is by a conducting wire or a conductor. (8) The high-frequency magnetic field according to claim 1, wherein the dielectric material is fixed to the outside of one of the two T-shaped conductor plates. Source/detector. (9) High-frequency magnetic field generation according to claim 1, wherein the dielectric material is fixed to the inside of the other T-shaped conductor plate of the two T-shaped conductor plates. ·Detector. (10) The high frequency magnetic field generator/detector according to claim 8 or 9, wherein the dielectric material is porcelain or a synthetic resin polymer.